Bottom Line:
Although uncommon, the procedures may result in tumor implantation along the needle tract, which is a major delayed complication.Implanted tumors usually appear as one or a few, round or oval-shaped, enhancing nodules along the needle tract on CT, from the intraperitoneum through the intercostal or abdominal muscles to the subcutaneous or cutaneous tissues.Radiologists should understand the mechanisms and risk factors of needle tract implantation, minimize this complication, and also pay attention to the presence of implanted tumors along the needle tract during follow-up.

Affiliation: Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.

ABSTRACTPercutaneous interventional procedures under image guidance, such as biopsy, ethanol injection therapy, and radiofrequency ablation play important roles in the management of hepatocellular carcinomas. Although uncommon, the procedures may result in tumor implantation along the needle tract, which is a major delayed complication. Implanted tumors usually appear as one or a few, round or oval-shaped, enhancing nodules along the needle tract on CT, from the intraperitoneum through the intercostal or abdominal muscles to the subcutaneous or cutaneous tissues. Radiologists should understand the mechanisms and risk factors of needle tract implantation, minimize this complication, and also pay attention to the presence of implanted tumors along the needle tract during follow-up.

Mentions:
Needle tract implantation is possible when the tumor is identified on imaging or physical examination in the perihepatic intraperitoneum, intercostal muscle, abdominal muscle, subcutaneous fat, or cutaneous tissue along the pathway of the needle. CT is the preferred imaging technique for evaluating needle tract implantation and the liver (7, 9). Although implanted tumors may have linear or elongated configurations (Fig. 1), they usually show one or a few, round or oval-shaped enhancing nodules along the previous needle tract (Fig. 2). The tumors can be located from the intraperitoneum through the intercostal or abdominal muscles to the subcutaneous or cutaneous tissues, with or without a linear arrangement (Figs. 1-4) (7, 9, 11). If the lesions grow, they conglomerate and form a relatively large mass (Fig. 3). Although the implanted tumors can reach diameters of 5 cm, they are usually smaller than 2 cm (7, 9, 13). On contrast-enhanced, triple phase CT, the implanted tumors may show hyperattenuation with hypervascularity or isoattenuation relative to the surrounding structures on the arterial phase. Thereafter, they show persistent enhancement with high- or iso-attenuation on portal and equilibrium phases, similar to the typical enhancement pattern (arterial enhancement, followed by washout) of HCC in the liver compared to hepatic parenchymal enhancement (Fig. 4) (7, 9). However, the contrast enhancement pattern may be influenced by the size of the implanted tumors and the characteristics of the primary HCC (9). Different enhancement patterns of implanted tumors and HCCs in the liver may occur due to different blood supplies between the liver and the surrounding tissue where the implanted tumor is located (7).

Mentions:
Needle tract implantation is possible when the tumor is identified on imaging or physical examination in the perihepatic intraperitoneum, intercostal muscle, abdominal muscle, subcutaneous fat, or cutaneous tissue along the pathway of the needle. CT is the preferred imaging technique for evaluating needle tract implantation and the liver (7, 9). Although implanted tumors may have linear or elongated configurations (Fig. 1), they usually show one or a few, round or oval-shaped enhancing nodules along the previous needle tract (Fig. 2). The tumors can be located from the intraperitoneum through the intercostal or abdominal muscles to the subcutaneous or cutaneous tissues, with or without a linear arrangement (Figs. 1-4) (7, 9, 11). If the lesions grow, they conglomerate and form a relatively large mass (Fig. 3). Although the implanted tumors can reach diameters of 5 cm, they are usually smaller than 2 cm (7, 9, 13). On contrast-enhanced, triple phase CT, the implanted tumors may show hyperattenuation with hypervascularity or isoattenuation relative to the surrounding structures on the arterial phase. Thereafter, they show persistent enhancement with high- or iso-attenuation on portal and equilibrium phases, similar to the typical enhancement pattern (arterial enhancement, followed by washout) of HCC in the liver compared to hepatic parenchymal enhancement (Fig. 4) (7, 9). However, the contrast enhancement pattern may be influenced by the size of the implanted tumors and the characteristics of the primary HCC (9). Different enhancement patterns of implanted tumors and HCCs in the liver may occur due to different blood supplies between the liver and the surrounding tissue where the implanted tumor is located (7).

Bottom Line:
Although uncommon, the procedures may result in tumor implantation along the needle tract, which is a major delayed complication.Implanted tumors usually appear as one or a few, round or oval-shaped, enhancing nodules along the needle tract on CT, from the intraperitoneum through the intercostal or abdominal muscles to the subcutaneous or cutaneous tissues.Radiologists should understand the mechanisms and risk factors of needle tract implantation, minimize this complication, and also pay attention to the presence of implanted tumors along the needle tract during follow-up.

Affiliation:
Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.

ABSTRACTPercutaneous interventional procedures under image guidance, such as biopsy, ethanol injection therapy, and radiofrequency ablation play important roles in the management of hepatocellular carcinomas. Although uncommon, the procedures may result in tumor implantation along the needle tract, which is a major delayed complication. Implanted tumors usually appear as one or a few, round or oval-shaped, enhancing nodules along the needle tract on CT, from the intraperitoneum through the intercostal or abdominal muscles to the subcutaneous or cutaneous tissues. Radiologists should understand the mechanisms and risk factors of needle tract implantation, minimize this complication, and also pay attention to the presence of implanted tumors along the needle tract during follow-up.